Dielectric Properties of CaTiO_3-Ca(Mg_<1/3>Nb_<2/3>)O_3 Ceramic System at Microwave Frequency

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The crystal structures and the microwave dielectric properties of the(1-x)CaTiO_3-xCa(Mg_<1/3>Nb_<2/3>)O_3 perovskite ceramic system have been investigated. The(1-x)CaTiO_3-xCa(Mg_<1/3>Nb_<2/3>)O_3 solid solution exhibited orthorhombic crystal structures for all compositions. As the x value increses from 0.2 to 0.8, the dielectric constant ε_r decreases from 109 to 36 and the unloaded quality value Q×f increases from 8600 to 39000(at 6.7GHz). The temperature coefficient of the resonant frequency(τ_f)varies from 298 to -30ppm/°C as the x value increases from 0.2 to 0.8. A new microwave dielectric material, 0.4CaTiO_3-0.6Ca(Mg_<1/3>Nb_<2/3>)O_3, applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ε_r〜54, a Q×f value 〜32000(at 6.7GHz)and a τ_f value 〜18ppm/°C. Further improvement of the τ_f value is expected by adjusting the x value of(1-x)CaTiO_3-xCa(Mg_<1/3>Nb_<2/3>)O_3 ceramics.
社団法人応用物理学会の論文
2000-12-15